LOCALIZATION IN CARBON NANOTUBES WITHIN A TIGHT-BINDING MODEL

We analyze the influence of defects on conductance, density of states, and localization in (N{sub a},N{sub a}) armchair carbon nanotubes within a tight-binding model. Using the transfer-matrix method, we calculate the reflection (related to the conductance) from a sequence of defects and relate its energy dependence near the Fermi level to the appearance of a quasibound state. This state is also seen in the density of states and in the energy dependence of the quasiparticle lifetime. We compute the localization length {xi}({omega}) as a function of energy {omega}. Comparison of {xi}(0) with the mean free path l{sub mfp} in the limit of small defect concentration c and small defect strength E leads to a simple approximate relation {xi}(0){approx}3l{sub mfp}=3{times}3aN{sub a}t{sup 2}/2cE{sup 2} (t{emdash} hopping integral, a{emdash} lattice constant). {copyright} {ital 1999} {ital The American Physical Society}